Detection and/or measurement of particles in a fluid is well-known, and such detection and/or measurement has heretofore been effected by a number of devices, including devices which illuminate a sample region to cause light to be scattered by particles in the fluid with the scattered light then being detected and processed to provide an indication and/or measurement of a parameter thereof, such as particle size.
In-situ measurement of particles in a fluid has been hertofore proposed and/or utilized for contamination control in connection with various process tools, including process tools used in semiconductor process environments.
Now known instruments using light scattering to size particles to thereby monitor contaminants are normally either intrusive type instruments wherein the sensing mechanism intrudes into the process environment (as is illustrated in FIG. 1 showing, typically, detectors 8 mounted on opposite walls of sensor unit 9 having laser beam 10 directed therethrough, with sensor unit 9 being inserted through aperture 11 into flow line 12), or are nonintrusive type instruments wherein the sensing mechanism is maintained outside the process environment (as is illustrated in FIG. 2 showing, typically, detection of light scattered by particles at sample region 14 within flow line 15 using reflector 16 to direct scattered light to detector 17 connected with processing circuitry 18 with reflector 16, detector 17 and processing circuitry 18 all being mounted outside of flow line 15).
Intrusive and nonintrusive type instruments, have been heretofore used, or suggested for use, under differing conditions, and either type of unit can, for example, be used to view a sample area, or region, in a process exhaust line (ie, pumpdown line). Intrusion type instruments, have, however, proved to be undesirable for at least some flow line uses due to necessary physical intrusion of this type of instrument into the flow line (in the case of an exhaust line, for example, the conductance of the exhaust line is reduced thereby changing the pumpdown characteristics for the process tool).
Both intrusive and nonintrusive type instruments, now known, have exhibited characteristics which can severely limit both performance and reliability of such instruments. In some cases, such instruments have been rendered ineffective in some process environments, particularly where such process environment has a contaminating or corrosive nature. Optical and electrooptical components that are exposed to such an environment can, for example, have contamination problems due to corrosion and/or deposition of/by materials from the process tool. This results in degradation of instrument performance and/or instrument failure depending on the severity of the contamination.
While purged gas has heretofore been used upstream from detecting instruments in an attempt to help shield such instruments from contamination, such purging often has failed to satisfactorily solve the problem and can, at least in some cases, adversely affect process operating parameters.
Now known instruments have also been singular instruments with a viewing section and a detecting section in the same housing. The singular nature of such instruments has resulted in imposition of undesirable restraints in use as well as precluding at least some types of improvements to the instruments, including, for example, heating of optics (since such heating would also undesirably heat other components, such as laser sources, detectors and associated electronics, often resulting in dramatically increased failure rates for such components) and/or easy instrument servicing or verification (since removal of the instrument requires a break in the associated flow line and hence requires process tool shutdown when the flow line break disrupts operation of the process tool as, for example, where the flow line break results in a break in vacuum).